Effects of pollutant discharges on the aquatic mammal populations of Terminos Lagoon, Campeche, Mexico

Abstract

Terminos Lagoon was made a protected ecosystem by the Mexican government in 1994, but it is also the most important center for oil extraction and transportation companies in the Gulf of Mexico, besides several rivers carrying on city effluents along with agricultural and cattle residuals into the lagoon. The main goal of this study is to analyze the potential for aquatic mammal species such as bottlenose dolphins, manatees and river otters to be environmental sentinels. While data showed that levels of heavy metals and pesticides contained in bottlenose dolphins blubber samples – lead (< 1.1 mg/l) and cadmium (< 0.08 mg/l) – were low, heptachlor epoxies showed the highest values (359.67 ?g/g), followed by endosulfan sulfate and methoxychlor,' p-DDE, which was recorded in a sample with concentrations of 239.542 ?g/g, along with p 'p-DDD and p' p-DDT, with values of 1.2 and 13.63 ?g/g, respectively. Analysis of heavy metals in Manatee bones showed that zinc, lead and cadmium presented higher concentrations (102.60 + 27.19 ?g/g, 14.54 + 1.77, ?g/g and 3.92 + 0.5 ?g/g, respectively). Values of both heavy metals and pesticides in samples were low compared to those recorded in other studies. Water quality analysis at the fluvial-lagoon system POM-Atasta found concentrations of BOD5 of up to 270 mg/l, COD 640 mg/l and SST 245 mg/l. These environmental and biological parameters, combined with the health assessment results for bottlenose dolphins, indicate that dolphins have a good health condition but human activities such as agriculture, livestock, fishing and boat traffic seem to have a chronic impact on the ecosystem and, subsequently, on the aquatic mammals found in Terminos Lagoon.